What Are Net Carbs?

I have type 1 diabetes, and my son recently gave me a package of sugar-free hard candy that was labeled "0 net carbs." The back of the package said, "To calculate net carbs, subtract the sugar alcohols from the total carbs in the product, because sugar alcohols have minimal impact on blood sugar." I am concerned and confused about this labeling.
Scott Winzeler, Gainesville, Florida

Madelyn L. Wheeler, MS, RD, CDE, FADA, CD, responds: The term "net carbs" came about when the "low-carb" food fad began a decade ago and companies were seeking a way to market their products as being low in carbohydrates. A food's total carbohydrate count (in grams) is arrived at by subtracting the grams of protein, fat, moisture, and ash from the food's total weight. What's left is the total carbs. On a nutrition label, the total carb count is required by the Food and Drug Administration (FDA) to include the full amount of grams from sugar alcohols and fiber. However, these carbs have less impact on blood glucose than others because they are only partially converted to glucose, or not at all, by the body. Some food companies started using the term "net carbs" and defined it to mean the total grams of carbohydrate minus the grams of sugar alcohols, fiber, and glycerine. This equation is not entirely accurate, because some of the sugar alcohols and fiber are absorbed by the body. In fact, about half of the grams of sugar alcohols are metabolized to glucose.

The term "net carbs" does not have a legal definition, and it's not used by the FDA or the American Diabetes Association. When you see it on a label, you should read the nutrition facts and ingredients list for more information. If you are not on intensive insulin management and do not count carbs, you don't need to do anything. If you are on intensive insulin management, count carbs, and manage your diabetes with carb-to-insulin ratios, you can:

1. Check the product's sugar alcohol content. If it is greater than 5 grams, subtract half the grams of sugar alcohols from the total carbohydrates and count this as the "available carbohydrate" for insulin adjustment purposes. However, if erythritol is the only sugar alcohol listed, subtract all of the grams of sugar alcohol.

2. Check the fiber content. Total fiber in foods comprises many different types of natural fiber and manufactured ingredients. They may vary in whether they are digested and how they affect blood glucose. If insoluble fiber is listed on the nutrition facts panel under "Total Carbohydrate," subtract all of the insoluble fiber from the total carbohydrates and from the total fiber grams. If the fiber quantity is still greater than 5 grams, subtract half the grams of dietary fiber from the total carbohydrates, and use the result as the available carbs for insulin adjustment purposes.